The present invention relates to a magneto optical recording medium used for optically recording and reproducing information.
In the art of optical memories, the magneto optical recording system has been put to practical use as an erasable memory which is capable of over writing and erasing. Presently, a thin film of an alloy composed of a rare-earth metal and a transition metal is most popularly used in view of its comprehensive properties, as the recording layer of the magneto optical recording media.
It has been disclosed to dispose a reflective layer on the recording layer of a magneto optical recording medium for improving the recording and reproducing performances of the recording medium when exposed to laser beam. It has been also proposed to dispose a heat insulating layer between the recording layer and the reflective layer for increasing the heating efficiency of the recording layer. It is possible to enlarge the power margin of recording light or to minimize the variation of sensitivity to recording pulse width by dint of the thermal effect of the said reflective layer or heat insulating layer.
There have been proposed various kinds of heat insulating layer and interference layer which is disposed between the substrate and the recording layer. However, there is yet available to ones which are well satisfactory in respects of adhesion to resin substrate, life-time under a high-temperature and high-humidity environmental, etc.
Thus, an offer of magneto optical recording medium which is excellent in layer adhesion to the substrate and long in life-time under high-temperature and high-humidity environments, that is, has excellent environmental resistance, and shows high sensitivity, CNR and power margin has been demanded.
As a result of the present inventors' studies in order to meet such a request, it has been found that in a magneto optical recording medium comprising, as laminated on a substrate, an interference layer, a recording layer, a heat insulating layer and a reflective layer, by using tantalum oxide for the interference layer and silicon nitride and/or silicon oxide for the heat insulating layer, the obtained magneto optical recording medium is markedly improved in adhesion between the substrate and the interference layer, suffers no decrease of life-time under high-temperature and high-humidity environments, that is, has excellent environmental resistance, and shows high sensitivity, CNR and power margin. The present invention has been achieved on the basis of this finding.